Spinal fusion (also called spondylodesis or spondylosyndesis) is a surgical procedure by which two or more adjacent vertebrae are joined or fused together. This method is primarily used to reduce or eliminate pain caused by abnormal motion of the vertebrae from conditions such as scoliosis, degenerative disc disease, spondylolisthesis, kyphosis, spinal stenosis, fractures, infections, tumors, and other degenerative spinal conditions or conditions that cause instability of the spine.
In interbody fusion, a commonly performed type of spinal fusion, a medical device called an interbody fusion cage or spine cage is surgically inserted between adjacent vertebrae to maintain spine alignment and disc height. Additionally, graft material harvested from the patient (autograft) or from a donor (allograft) is inserted into the intervertebral space with the spine cage to encourage the natural osteoblastic process and resulting fusion between the endplates of the vertebrae. Pedicle screws may also be used to augment the fusion.
Interbody fusion methods that access the vertebrae through the patient's back (rather than an anterior approach through the abdomen), such as the posterior transpedicular approach, typically involves muscle dissection from the back of the spine in order to create enough space to insert one or two spine cages. The spine cage has a diameter that is equal to the desired distance by which the vertebrae are to be separated, and so significant manipulation of the anatomy surrounding the vertebrae must be performed. Not only are the spinal muscles stretched, moved, or cut, but parts of the ligament flava, which connect the laminae of the adjacent vertebrae, around the implantation site are cut away from the laminae and removed. Additionally, parts of the laminae and/or pedicle above and below, and parts of the facet joints on either side, of the implantation site are removed to increase access. Finally, a substantial portion of the intervening disc is removed and the endplates of the adjacent vertebrae rasped or roughened.
Unsurprisingly, the posterior transpedicular approach is very traumatic to the patient. Not only is there a long recovery time, but the patient may experience significant amounts of pain immediately following the procedure. Further, the procedure compromises the ligaments and muscles that aid in spinal stability, strength, and function. Other known procedures, such as transforaminal interbody fusion methods (TLIF), posterior lumbar interbody fusion methods (PLIF), and lateral and anterolateral transpsoas fusion methods may be equally traumatic to the patient. For example, such procedures may easily result in nerve, ligament, bone, and/or soft tissue damage.
It is therefore desirable to provide a spinal implantation device and method that requires less anatomical manipulation, a smaller insertion space, and is less traumatic than currently known methods.